Cancer is known to occur because of some abnormality in a gene. A change or abnormality in the gene at its transcription level, in particular, is regarded as a major cause of cancer ("Science" Vol. 222, 1983, pp. 765-771). To elucidate the mechanism of onset of cancer, the acquisition of a protein variedly expressed during carcinogenesis and a gene encoding the protein, or a protein different in the state of expression among tissues and a gene encoding the protein has been performed eagerly since about 1980. For example, .alpha.-fetoprotein and CEA (carcinoembryonic antigen) are known as cancer-specific proteins which were acquired by biochemically analyzing a carcinomatous tissue, and searching for its difference from a normal tissue.
Nevertheless, only a part of carcinogenesis mechanism has been clarified so far, thus leaving a demand for further elucidation of carcinogenesis-related genes and proteins. Also demanded is a novel method of diagnosing cancer using these carcinogenesis-related genes and proteins.